jtag2updi VS AVR-Guidance

Uploaded Jtag2Updi code to Arduino Nano

Uploaded [Jtag2Updi](https://github.com/ElTangas/jtag2updi) code to Arduino Nano

I've had some experience with wrangling UPDI based 8-bit micros before. UPDI is a different beast compared to AVR-ISP based programming, it uses only 1 data pin instead of the usual SPI's 3 (MOSI, MISO, SCK). You just have to wire the two devices according to the jtag2updi official documentation here, then select the correct board type (specific core that targets the 1616, I assume you're using SpenceKonde/megaTinyCore?), the correct programmer type (JTAG2UPDI), and upload away!

I haven't used the 1626 yet, I only have experience with the ATmega328 really. Isn't UPDI just a specific ISP protocol? I might be mixing up the terms here. I was planning on using jtag2updi which has support for the 2-series.

I like how it doesn't require any expensive proprietary programmer, an Arduino Nano is all you need...

Check out the newer attiny chips......cheap, available, and LOW POWER. No external crystal or other components required. Programmable via Arduino IDE.,,see: https://github.com/SpenceKonde/megaTinyCore You can use any arduino as a programmer (JTAGTOUPDI) or make one with a cheap serial adapter: https://github.com/SpenceKonde/AVR-Guidance/blob/master/UPDI/jtag2updi.md

For Serial UPDI attach either a diode or resistor between RX and TX, then connect RX to UPDI PIN, along with and VCC and GND. https://github.com/SpenceKonde/AVR-Guidance/blob/master/UPDI/jtag2updi.md

I own a PICKIT4, so normally I would just breakout Vcc, Gnd, and UPDI pins and directly connect my PICKIT to it. This time though my friend recommended me to also include a SerialUPDI circuit on board to accommodate Arduino users (and ones without PICKIT in general). The part related to SerialUPDI are JP3, JP4, D35, and R5.

Yup, that should do the trick. You might want to give this guide a good read-through. It has some chip-specific tips (search for FTDI) and general recommendations for wiring and removing the Rx LED if it gives you troubles.

Choice of hardware

You can use RX/TX with the UPDI interface directly, see https://github.com/SpenceKonde/AVR-Guidance/blob/master/UPDI/jtag2updi.md. You should at least add a resistor on the line. Then you'll be able to program it with pymcuprog in serial mode, without a bootloader.

ISP looks a lot like spi. Updi is asynchronous uart. It's a lot different and I would recommend looking at serial updi.